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1

The food of roach, Rutilus rutilus (Actinopterygii: Cypriniformes: Cyprinidae), in a biomanipulated water supply reservoir

100%
Zapletal T., Mares J., Jurajda P., Vsetickova L.
Acta Ichthyologica et Piscatoria
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2014
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tom 44
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nr 1
Background. Roach, Rutilus rutilus (Linnaeus, 1758), is an omnivorous fish species that is able to utilise a range of food resources. Both juvenile and older roach can negatively affect zooplankton abundance in freshwater bodies of water; hence populations are often reduced (biomanipulated) in order to increase zooplankton populations. The aim of this study was to assess the roach diet after large-scale removal of cyprinids (bream, roach) from a reservoir. The study was done to clarify the roach diet after three years of intensive reduction of cyprinid fish and also to find out how the roach feeding behaviour impacts the quantity of filtering zooplankton. As such, this study may help to explain more general relations within the aquatic food web and specify the roach diet during the vegetative season (from spring to autumn). Materials and Methods. This study was undertaken at the Hamry water supply reservoir in the Czech Republic. Samples of macrozoobenthos, periphyton, and zooplankton were collected as representative food resources. Fish were caught using a 100-m littoral beach seine during the April to October growing season in 2011. Supplementary fish were caught using a pelagic Nordic gillnet in August and September 2012 and a 15-m beach seine in June and August 2012. Gut contents were preserved in 4% formaldehyde for later laboratory analysis (frequency of occurrence, index of preponderance, index of gut fullness). Results. ‘Detritus’ was the major component found in roach guts, with no difference observed in age category or locality (littoral vs. open water areas). Significant differences were observed, however, between younger (0+ and 1+, 36–92 mm) and older (>3 years, >92 mm) fish. The 0+ and 1+ age groups also fed on zooplankton (P < 0.008), accompanied by Chironomidae (1+), while diet of older roach (3–4+; 6–8+) included macrophytes and periphyton, together with Cladocera (fish from open water; P < 0.008). Conclusion. The results demonstrate that detritus was the main ‘dietary’ component of roach during the growing season, with macrophytes and periphyton as complementary dietary items. Zooplankton was an important dietary component of mainly younger roach age classes. Roach appear to be an important component in ichthyo-eutrophication of the Hamry Reservoir, mainly through transfer of phosphorous from plants to water.
2

Effects of semi-intensive carp pond farming on discharged water quality

100%
Vsetickova L., Adamek Z., Rozkosny M., Sedlacek P.
Acta Ichthyologica et Piscatoria
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2012
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tom 42
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nr 3
Background. Fish pond management can substantially modify the hydrological regime and ecological quality of receiving waters (usually rivers, canals, and ponds downstream in an interconnected system) with potentially positive or negative impacts on watershed functioning. To evaluate these effects with respect to carp pond management, the environmental impacts of semi-intensive farming on discharged water quality were monitored at four differently managed carp ponds, differing in trophic status (two eutrophic and two hypertrophic ponds). Materials and Methods. Fundamental determinants of pond inflow and outflow water quality were monitored monthly from April to October 2009. Water temperature, pH, and dissolved oxygen concentration and saturation were measured in situ whilst hydrochemical and microbiological parameters were assessed in the laboratory. Results. Compared to the inflow water, in the effluents there was a significant decline in numbers of bacterial loading indicators (Escherichia coli, enterococci, faecal coliform and mesophilic bacteria) in the outflow water. In ponds with the poor quality inflow water (downstream of water treatment plant discharges), a significant decrease was also registered in nutrients (N-NH4, N-NO3, total nitrogen, P-PO4, and total phosphorus) and organic loads? (five-day biological oxygen demand, chemical oxygen demand) of pond effluents. At the pond supplied with good quality river water, however, the same determinants showed that effluent water quality worsened significantly. Total organic carbon and suspended solids increased in effluents of ponds with high fish biomass stocked. Conclusion. The results demonstrate that, during the growing season, properly managed carp ponds represent ecosystems with high self-cleaning ability. They may play an important role in the nutrient balance, storage and trapping in agricultural landscape with high population density.
3

Response of small-stream biota to sudden flow pulses following extreme precipitation events

88%
Adamek Z., Konecna J., Podhrazska J., Vsetickova L., Jurajdova Z.
Polish Journal of Environmental Studies
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2016
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tom 25
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nr 2
Extreme discharge rate increases in small streams caused by sudden extreme precipitation events are classifi ed as small-scale pulse-type disturbances. Small highland brooks in agricultural landscapes (arable land and meadows) are frequently characterised by extremely low flows during normal conditions, plus the rare appearance of high-flow events that periodically may reset their ecosystems. We studied two small highland brooks to assess the impact of extreme discharge rates (flow pulses) upon periphyton, macrozoobenthos, and fish assemblages. No distinct changes were recorded in composition of periphyton assemblage or fish (brown trout, Salmo trutta m. fario) occurrence following such flow pulses. Cyanobacteria, however, were absent following a flow pulse, while growth appeared to be boosted in green algae (Chlorophyceae). Similarly, there was no negative response observed in macrozoobenthos communities, with density, diversity, taxa richness, and saprobic indices remaining either more-or-less unchanged or considerably enhanced following high-discharge episodes. These observations were confi rmed through Sörensen’s similarity indices, which indicated no signifi cant change in either periphyton or macrozoobenthos following such episodes.
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